Jan Carlin's Blog
A Swede in the digital diaspora

I recently came across a situation where I needed to see the stack trace in Forms since I had received a Java Exception in a PLSQL Exception section. It turned out it isn't as easy as calling getStackTrace on the java.lang.Exception and loop through the resulting Java array and do toString on each. Here is what you have to do:

First you need to import these classes:
java.lang.StackTraceElement
java.lang.Exception

To do that, you type in the full class name in the Java Importer dialog.

Then you click the Import button and a PLSQL will be created to make it possible to call out to the two classes.

Then you write this code in the PLSQL Exception handler:

declare
  excep ora_java.jobject;
  stack_trace ora_java.jarray;
  stackTrcElement ora_java.jobject;
begin
  ...
exception
  when ora_java.java_error then
    message('Error: '||ora_java.last_error);
    return 0;
  when ora_java.exception_thrown then
    excep:=ora_java.last_exception;
    :control_blk.excp:='Exception: '||Exception_.toString(excep);
    --Get an array of StackTraceElement from the Exception
    stack_trace:=Exception_.getStackTrace(excep);
    --Loop over all the Elements
    for i in 0..ora_java.get_array_length(stack_trace) loop
      --Get each Element
      stackTrcElement:=ora_java.get_object_array_element(stack_trace, i);
      --Make a string out of it and add it to the error field
      :control_blk.excp:=:control_blk.excp||(10)||
        stackTraceElement.toString(stackTrcElement);
    end loop;
  return 0;
end;

The Exception_.getStackTrace(excep) returns an array of StackTraceElements. One of its methods is the toString that we need. In this example I iterate over the array and fill up a multi-line Forms field with the resulting strings. The result looks very much like the familiar stack traces you see in JDeveloper or any Java tool when Java throws an Exception. The field :control_blk.excp is a temporary field that I added to a control block in Forms to be able to see the stacktrace while I was debugging.